Compared with traditional cooling methods, vacuum pre-cooling has the following advantages:
1)fast cooling speed.The outstanding characteristic of vacuum pre-cooling technology is its fast pre-cooling speed. For most leafy vegetables, even after packaging before pre-cooling, the temperature can be reduced to 4-5 degrees in 20 ~ 30min.The vacuum precooling effect on broadleaf vegetables is quite obvious.
2)even cooling.Due to the balanced pressure at each point in the pre-cooling box, the moisture in the fruits and vegetables can evaporate and absorb the stored field heat in the body at the same time, which makes the cooling of fruits and vegetables in the box very even.
3)low energy consumption.There is no need to remove the cooling medium in the system, and the vacuum minimizes the heat input from the outside world.
4)clean.Because air can only enter when the vacuum cooling chamber is opened, keeping the fruits and vegetables clean.During the cooling process, precise temperature control can be achieved through the control of absolute pressure, so that the product can be maintained at 1 ~ 3 degrees.
Main disadvantages of vacuum precooling:
1)weight loss due to moisture loss.Vacuum precooling will inevitably reduce the weight while lowering the temperature.Weight loss can be prevented by adding water during precooling.But the equipment is expensive and requires packaging that adds water.The vacuum precooling process and subsequent water vapor loss can also adversely affect food quality factors such as texture, color and perceived product characteristics.
2) high initial investment in equipment.Due to the high cost of equipment, the processing process is not suitable for those foods that require additional refrigeration to ensure cooling capacity.The cost of vacuum pre-cooling is higher than other pre-cooling, even the initial investment is very high.